Alkylation method



Patented July 9, 1 946 land, Mich., asslgnors to TheY Dow Chemical Company, Midland Mich.,Y a' 'corporation of kMichigan *i j,

' Appxiceaonocteber 7, 194s, serial No. '505,352v

matic compounds. employed as reactants inthe process have'the general `formula:

wherein X and Y each represents hydrogen, or a halogen atom, e. g. chlorine Vor bromine, or an alkyl radical. Such reactants,` and also the alkylated reaction products, are members of the benzene series and, for convenience, may be referred toas benzene compounds. f

Th` reaction of olenes with benzene compounds `in the presencer of aluminum chloride is well'k'nown andA is applied industrially in the man` u facture of "ethylben'zene '.l'he reaction to producemethylbenzene is usually carried out at at'- mospheric pressure or thereabout and at temperature's between r50 and '80`C. in the'pre'sn'ce of'aminor, but appreciable, amount of aluminum chloride as catalyst.v The aluminum chloride is employed in a concentration corresponding to two per cent or moreV of the weight of thebenzene reactant'i. e. in. amount corresponding to kat least 0,01 molecular' equivalent of AlCh per mole of benzene, since smaller proportions areineilectual under such usual reaction conditions'. Aithough other reaction temperatures and pressures have in certain instances been tested, the aluminum chloride catalyst has, insofar as 'we are aware, always been used in concentrations as high as those just mentioned. Usually. a small amount of hydrogen chloride,v or a compound capable of forming the same in situ in the reaction mixture, is also added as a catalyst promotor. y

During use in the reaction, the aluminum chloride forms an addition compound with other ingredients of the mixture. The addition compound, variously known as a complex catalyst, a catalyst complex,V or as a catalyst sludge, possesses a high catalytic activity, but is only sparingly soluble in the reaction mixture. Accordingly, in usua1 practice, the mixture is stirred or otherwise agitated during the reaction and'is subsequently permitted to settle into a lower layer of the complex catalyst and an upperlayer of the alkylated aromatic products. The upper layer is separated and treated to remove the small amount of dis- 16 claims.- (c1. esci-7.671): t

tlled to separate the products.- The icatalyst layer of the reaction mixture may bereemployed in the alkylationreaction, but after being recycled a number of`times, it losesV its activity and is discardedjg'. o A. plurality of alkylatedlaromatic products, e. g. a mixture ofrmono-ethylbenzene and polyethylbenzenes', is frmedfin the reaction. When a mono-alkyl aromatic compound is desired as the product, vthe varomaticreactant is used in molecular excess overthe olenein order that the formation of such productmay be favored.. However, even when using the aromatic reactant in excess, polyalkylated products are formed in considerable amount.' For instance, in thev manufacture of ethylbenzene, althoughy from `2 to 6 molecular Veqiii'vaatlents ofjbenzene are usually employed per moleof ethylene, the yield of ethylbenzene seldom, if ever, exceeds 65 per cent of theoretical" and polyethylbenzenes areV formed Y in considerable amount. Thefpolyethylbenzenes may be cut 1back, to'ethylbenzene by being vreacted with benzene inthe presence of aluminum chloride, but this involves extra operations. It isdesirable that the proportionof the products which need be cut back be as small as possible.

,Inabonti'nuous'process for the manufacture of ethylbezene under. the usual operating conditiohsjust described, Vlarge and expensive reactors are requiredlin order to provide ample time forffthealkylation reaction while producing the productiin thel amounts required and alsoin order to cutl,back to ethylbenz'enethe considerable amounts -of polyethylbenzehes which are formed. Also, although the proportion of catalyst present in the alkylation mixture at any instant may be quitefsmalLthe total amount of aluminum chloride vconsumed per year is large. For purpose of economy, and in order Vto'conserve on aluminum chloride which,Y atppresent, is availabler in re- .stricted amountaa method' whereby the reaction may becarriedout with smaller'amounts of the catalyst is desired.

"Itis v`an object of thisinvention to provide an improved Ymethodof alkylating hydrocarbons or halohydrocarbons of the benzener series with oleflnes, whereby .theproportion of catalyst required for the reaction may be reduced below that heretoiore considered necessary and whereby .the reactionjmaybe carried' out rapidly and continuouslyin apparatus'Vv of vsimple construction. Another object is to vprovide such methodwhereby aPlQfiOalkYljaromatcicompund may be produced idirectly -inillnusually,v high yield, relative served catalyst, after whaha-.is fpreuornally c15- 55 tajine p'lylkylacec products., A further object 1s to provide such method whereby the alkylation reaction may be carried out smoothly, rapidly and in continuous manner using apparatus of simple construction, e. g. a tubular autoclave. Ortner objects will be apparent from the following description of theA invention.

We have foundthat byA carrying the"read-lV tion between anolenne and a benzene compound,

i. e. a hydrocarbon or nuclear halogenated hy,-

drocarbon of the benzene series, at temperatures above 90 C- and under a pressure suicientto;

liquefy the mixture, the proportionof catalyst required for the reaction may 'bereduced great'- ly. We have further foundth'at when a mixture of an olene and a molecular excess of an aro?" matic hydrocarbon is reacted under such conditions, a monoalkylated` aromaticv 4compound isf formed in higher yield, relative to the, polyalkylated products, than when the reactiori`is"` usual reaction conditions. o The reaction between an 'clef-lne and 'a bencarried out under the hereinbefore Vmentioned zene compound may be carried out'batchwise, butis advantageously carried out in continuous manner. Similar reaction temperatures and proportions of the reactants and catalyst'are employed regardless of which procedure is followed'.

The accompanying drawing is -a flow sheet pressure into admixture with one another at rel-l ative rates of cw such that the mixture contains a molecular excess, e. g; from 2-6 molecular equivalents, of benzene per mole of the ethylene. Prior to l or after admixing the reactants, aluminum chloride is added in amount corresponding to less than 1.2, e g. from 0.3 to 1.0 and preferably from 0.3 to 0.7,rper cent ofthe weight of the benzene reactant. In other words, less than 0.007, e. g. from 0.00175 to 0.00584, and preferably from 0.00175 to 0.00437, molecular equivalent of aluminum chloride (on la Vbasis of the formula AlCla) is employed per mole 'of the aromatic reactant. The aluminum chloride is advantageously added by passing the benzene reactant, orv the reaction mixture,` through a bed of granular aluminum chloride :at the rate necessary to dissolve the required amount of catalyst.' practice, the aluminum' chloride is ,usuallyv dissolved by warming the benzene, e. gyto from 30 to 50 C., and passing'it through suchbed prio-r to admixing the ethylene therewithfj' i The reactants and the catalyst are preferably employed in as nearly anhydrous condition as possible. However, a minor amount of moisture, e. g. an amount corresponding to one or twoper cent of .the weight 'of the dissolved aluminum chloride, may be tolerated. Itshould'be mentioned that in Friedel-Crafts reactionsI between olefmes and aromatic hydrocarbons, it has heretofore been usual practice to add a small amount of hydrogen chloride or an alkyl chloride as a catalyst promotor and such promotor may, if desired, be added in practice of this invention. However, the alkylation reaction occurs satisfactorily under the reaction conditions herein disclosed in the absence of suchadded promotor and the latter may be omitted.

The mixture of ethylene, benzene and the caltalyst is passed at a liquefying pressure, e. a pressure suiicient to maintain vthe same in liquid form, throughv a tubular' autoclave or 'otherri actor where it is heated to a reaction temperature of at least 90 C. and preferably from 100 to 200 C. Somewhat higher temperatures, e. g. 220 C., may sometimes be used, but are not recommended. Under such preferred conditions,

the vallgylation reaction occurs rapidly and is usually` complete' in from 5 to 1`5 minutes. The rate of now through the reactor is preferably such as to permit substantially complete consumption 'ofV the o-lene reactant. outataipressure of at least 300 pounds per square The reaction is carried inch, gauge, preferably from 600 to 1200 pounds persquarefinh' yorhiglrier, when using ethylene las 4areacta'rrtf-y In similar reactions involving the use of propyleneror higher olenes, instead of ethylene, lower pressures, in some instances as lowia's50 `pounds per soluarei inch, may be employed.- In any instance, the pressure should be sufficient to maintain the reaction mixture largely in liqueed form so that the major part, and preferably" all, ofi the olefin is dissolved in the aiferriatie-i reactant." The reactor 'employed is preferablyfconstructed of, or lined with, a substance resistant to {corrosion'by acids. An autoclave lined WithSni'CReL-astainleSs steel, or glass, or 'constructed/of one lof said metalsr may be used. ""'f'l The mixture flowing from the reaction Zone is cooled, e. g, to below 5 0? C., and is passed through a valve for releasing the pressure. The ethylated benzene products may be distilled directly from the reacted mixturefand the residual catalyst be Areturned to the reaction, or the catalyst may first bre'removed in'any ofthe usual ways, e. g.. rr'echanically,'` when a portion of the catalyst separates asa distinctlayer, or by washing4 with water oran aqueous alkalisolution, or by adding ammonia v toformz a precipitate, etc., and thel ethylated 'benzeney products may thereafter be separaterl'by distillation. Usually the productsareurecovered in' somewhat higher yields when the catalyst is removed before distilltheproducts. The distillation is ordinarily carried out in such manner as to separate the ethylbenzene from polyethylbenzenes, e. g. diethylbenzene andtriethylbenzene. By operating as just fdescribed, "'ethylbenzene may be produced directly in a yield 'of 80 per cent of theoretical or higher, basedon the ethylene employed. Also, ed molecular'equivalents `orgrnore of ethylene maybe reacted *per mole of the aluminum chloride' catalyst. e A 1 f 'The yield' may be further improved by reactingjthe polyethylbenzenes with benzene in the presenceiof 'aluminum chloride to form an added amount ofethylbenzene. The procedure for carryligout such dealkylation reaction is well known and need'not. berg-iven in detail. Instead of carrying. out .the dealkylation y'reaction separately from the alkylatinreaction, the polyethylben- Zenes may be returned to the alkylation reaction where they serve to suppress the further formation'of polyethylbenzenes and to directthe reac't'ionto the formation vof ethylbenzene in increased yield. f. The ,process may, Vif desired, be modied in otherways.` For instance, in placeof fresh aluminum chloride, the complex catalyst sludge from aprior'Eriedel-Crafts reaction may be used as such, orV in adrnixture with `fresh aluminum chloride, to E catalyze the reaction. Such catalyst sludge is, of. coursefless active than aluminum chloride fitseli` 'and' the latter is most convenientlyemployed.A However, when operating in the foregoing continuous manner, the reaction liquor winlehotye.A g. atico-200 C.; may 'be caused to'floWl from `the tubular reactor through' vated, catalyst in the reaction zone, and is treated tofree the polyethylbenzenesf-of the catalyst associated therewith. The' polyethylbenzenes` thusv recovered Vvmay be Vadmixed with lthe' Vbenzene starting material andbe returnedto thereaction zones.Y The benzene and ethylbenz'ene mixture oiltairledY as the distillate in the ash dis-'- tillation operation is fractionally distilled 'to sep-v arate the ethylbenzene product".V "The recovered benzene may be reemployed in the process.

For purpose of clarity, vtheinventon has 'been .explained with. special reference to the prepara'- tionsof ethylbenzenepbutit maybe applied in producing other alkylatedbenzene compounds. For instance, by increasing the 'molecular ratio of ethylene 'to benzene over those hereinbefore recommended, a polyethylb'enzene, e. g.-diethylben zene or triethylbenzene,-may/-be'producedv as a principal product. Also, the methodmay be employed in reacting propylene with ethylbenzene to form isopropyl-ethylbenzene; in reacting propylene with benzene to form isopropylbenzene or a polyisopropylbenzene; inv reacting .butylene with benzene to form a butylbenzene or a polybutylbenl zene; in reacting ethylene -with chlorobenzene to form ethyl-chlorobenzene or diethyl-chlorobenzene; in reacting -ethylene withbromobenzeneto form ethyl-bromobenzene Aor diethylbromobenzene; or in reacting propylene withchlorobenzene based on the ethylene.

6: therefrom. AThe 'gasesthus vented naa e volume-of approximately fone liter at atmospheric pressure andcontained little; if any.' ethylene.' The reaction mixture 'was removed from the bombl and Washed successively. with water and with a dilute aqueous sodiumlhydroxide solution to remove the catalyst. The mixture was then fractionally distilled, whereby there were. obtained 341 grams of unreaoted benzene, 268 grams of ethylbenzene and 77 grams of polyethylbenzenes (largely diethyl-1 benzene) .f It was found that 153 molecularA equivalents of .ethylene had been reacted per mole of aluminum chloride (AlCh) employed. The yield of ethylbenzene Was 80 per cent of theoretical,

. Example 2 vA solution of. 377.65 kilograms (483 moles) .of benzene vand .750 grams.(10.6 moles) vof ethyl chloride was pumpedunder pressure through a heatingV coil, whereit was warmed to between and .45? vC., .and thence through a chamber con- -tainingl granular aluminum chloride. .The rate,V

of flow through said chamber was such that the. liquor dissolved 134 grams of aluminum chloride,

Y an amount corresponding to 0.36 per cent of the weight ofthe benzene. .Ethylene of 94-per cent purity was fed, underza pressure of .600*'pounds per square inch, into admixture with the liquor flowing from the above-mentionedV chamber. A total of 2886 grams (103 moles)l of ethylene (on a basis of the pure compound) was thus added.

to formisopropyl-chlorobenzene or di-isopropylchlorobenzene; etc. The method ls particularly advantageous when employing ethylene or prolpylene as the oleiine reactant.

The following examples describe certain Ways Vinwhich the principle of the invention hasbeen applied, but are not to beconstrued as limiting its scope.

Example-1 Y lr* hydrous benzene. Ethylene of 94 per cent purity Y was then passed into the bomb until the pressure inside the bomb was 300 pounds per square inch at 20 C. The bomb was thenclosedand heated, while rotating the same, so that the temperature was increased from 20 tov 115 C. in 25 minutes and from 115 to 200 C. in 55 minutes. The bomb was maintained at 200 C. for20minutes, hence the total time of heating was approximately 1 hour 40 minutes. During heating the vapor pressure inside the rbomb increased in the first 25-rninute period fromthe initial pressure of 300 pounds per square inch at 20 C. to 580Y pounds at 115 C. Thereafter thepressure decreased to only 180 pounds per similare-inch at a temperature of 200 C. at the close ofthe heating period. The bomb was then, cooled to about room temperature andV unreactedgases.. were. rented Since both the ethylene and the jethyl chloride are capable of reacting to ethylate benzene, the* ethyl chloride may be considered as equivalent to ethylene. Accordingly, the molecular ratio of benzene to ethylene plusthe ethyl chloride was Y4.62. The solution of ethylene, benzene, ethyl chloride andaluminumvchloride was-passed undera pressure of about 600 pounds per square inch and at a ratelof approximately 3.6 liters per hour through a nickel tubular autoclave of inch internal diameter vand of 600 cubic centimeters capacity while heating the autoclave in an oil bath at 200 C. The contact time, i. e. the time required for an infinitesimal portion of the reaction liquor toY travel through the autoclave, was vapproximately 10 minutes. As the liquor flowedv from the autoclave it was cooledto approximately room temperature and then passed through a valvefor releasing the pressure. Approximately 141 liters of unreaoted gas were vented from the reacted mixture. The amount of gas thus vented corresponded to approximately 6 per cent of the volume of the ethylene of 94 per cent purity which had been used as a starting material; hence it was evident that substantially all of the ethylene, had reacted. Thereaction mixture was washed successively with water and a dilute aqueous sodium hydroxide solution and fractionally distilled. There were obtained approximately 27.5 kilograms (352 moles) of unreaoted benzene, 10.34 kilograms (97.5 moles) of ethylbenzene, and 1.9 kilograrnsof higher boiling products (largely diethylbenzene-together with some triethylbenzene). The yield of ethylbenzene was 85.8 per cent of theoretical, based on the combined amount of ethylene and ethyl chloride used as starting materials. A total of. 113.5 molecular equivalents of ethylene and ethyl chloride were reacted per mole of AlCla.

Example 3f Benzene was ethylatedy in continuous manner by procedure similar to that vdescribed inEXam- :rimarret-` ple 2, except that no ethyl chloride or hydrogenv chloride was added to the reaction mixture;- in place of benzene alone, a mixture ofapproximately 90 per cent by weight benzene and 10 per cent diethylbenzene was used asa starting material; and the amount of aluminum chloride dissolved in the reaction mixture corresponded to 1.1 per cent of the combined weight'of the benzene and the dethylbenzene used as'starting materials. The molecular ratio of benzene to the ethylene consumed was approximately 2:4. The reaction was carried out at a temperature of 200 C. under a maximum pressure of about 550 pounds per square inch. The products were separated as in Eixample 2. The diethylbenzene recovered from the mixture was slightly less than that initially employed; hence, no diethylbenzene was formed in the reaction. The ethylated benzene products were obtained in the relative proportions of 10 molecular equivalents of ethylbenzene to one molecular equivalent of diethylbenzene to only 0.247 molecular equivalent of higher boiling material (calculated as being triethylbenzene).

Eample 4 A stainless-steel bomb of 1.7 liters capacity was charged with a mixture of 624 grams (S moles) of benzene, 1.1 grams of ethyl chloride and 1.6 grams (0.012 mole) of aluminum chloride. Propylene was fed into the bomb under a pressure of 60 pounds per square inch, gauge, until the mixture was saturated therewith. The bomb was closed and heated gradually, while rotating the same, to 200 C. and then cooled to room temperature, It wasr noted that the mixture within the bomb was at approximately atmospheric pressure, indicating that practically all of the propylene'had been reacted. The bomb was opened and discharged. The reacted mixture was found to weigh 725 grams, indicating that 98.3 grams (2.34 moles) of propylene had been consumed. The mixture was Washed successively with water and a dilute aqueous sodium hydroxide solution, for purpose of removing the catalyst, and fractionally distilled. There were obtained 490 grams (6.28 moles) of unreacted benzene, 172 grams (1.43 moles) of isopropylbenzene, and 63 grams of higher boiling products, largely di-isopropylbenzene. The yield of isopropylbenzene was 61 per cent of theoretical, based n the propylene. The molecular ratio of propylene consumed to aluminum chloride em ployed was 195.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regards the meth- 8. gaseousolelne and aluminum chloride'in amount not exceeding 0.007 of the molecular equivalent of the aromatic compound, and heating the mixture at a reaction` temperature above 90 C. under a pressure sufficient to maintain it in liquefied form.

2. In a method of alkylating an aromatic compound having the general formula:

--X da wherein X and Y each representsa memberof the group consisting of hydrogen, halogens, and alkyl radicals, the steps which consist in forming a mixture of said aromatic compound,` an oleiine having not more than three carbon atoms in the molecule, and aluminum chloride in amount corresponding to between 0.00175 and 0.00584 of the molecular equivalent of the aromatic compound, and heating the mixture 4to a reaction temperature above 90 C. at a superatmospheric pressure suflcient to liquefy the mixture.

3. The method as described in claim 2, wherein the aromatic reactantis employed in molecular excess over the olene and the reaction temperature is between about 90 and about 200 C.

4. In a continuous method for alkylating an aromatic compound having the general formula:

wherein X and Y each represents a member of the group consisting of hydrogen, halogens, and alkyl radicals, the steps of passing said aromatic compound over solid aluminum chloride at a rate such that between 0.00175 and 0.007 molecular equivalent of aluminum chloride is dissolved per od herein disclosed, provided the step or steps i wherein X and Y each represents a member of the group consisting of hydrogen, halogens and alkyl radicals, the steps of forming a lqueed mixture of the aromatic compound, a normally mole of the aromatic compound, admixing with the resultant solution an olene having not more than three carbon atoms in the molecule, the mixing being carried out under a pressure suflcient to liquefy the mixture, and passing the mixture through a reaction Zone where it is heated to a reaction temperature above C. while at a pressure suflicient to maintain the same in liquid form.

5. The method as described in claim 4, wherein the aluminum chloride is employed in a proportion corresponding to between 0.00175 and 0.00584 of the molecular equivalent of the aromatic reactant, the reaction mixture is heated to a reaction temperature between 90 and 200 C., the reaction mixture is cooled and brought to atmospheric pressure as it flows from the reaction zone, and an alkylated aromatic product is separated from the mixture.

6. The method as described in claim 4, wherein the aluminum chloride is employed in a proportion corresponding to between 0.00175 and 0.00437 of the molecular equivalent of the aromatic reactant, the latter is employed in molecular excess over the olene, the reaction mixture is heated to a reaction temperature between 90 and 200 C. and is cooled and brought to atmospheric pressure as it flows from the heating zone, a mono-alkylated aromatic product is separated from the mixture, and polyalkylated aromatic products are recycledjto the reaction zone.

Y 9 7. In a continuous method of alkylating an aromatic compound having the general formula:

cooling the reaction mixture and vbringing it to atmospheric pressure as it ows from said zone, distilling the lower boiling alkylated aromatic product from the reaction mixture, returning a portion of the residual mixture of complex catalyst and polyalkylated products to the reaction zone, and while continuing the foregoing operations introducing aluminum chloride together with the reactants and withdrawing complex catalyst from the reaction system at rates such that the mixture in the reaction zone contains be- Y tween 0.00175 and 0.007 molecular equivalent of aluminum chloride in the catalyst per mole of the aromatic compounds.

8. In a method of ethylating an aromatic compound having the general formula:

wherein X and Y each represents amember of the group consisting of hydrogen, halogens, and

alkyl radicals, the steps of forming a liqueed mixture of the aromatic compound, ethylene and aluminum chloride in amount not exceeding 0.007 of the molecular equivalent of the aromatic compound, and heating the mixture at a reaction temperature above 90 C. under a pressure sufcient to maintain the mixture for the most part in liquefied form. Y

9. In a method of ethylating benzene, the steps of forming a liquefied mixture of ethylene. benzene, and aluminum chloride in amount corresponding to between 0.3 and 1.2 per cent of the Weight of the benzene, heating the mixture to a reaction temperature between 90 and'200 C. while at a pressure suiiicient to maintain the same largely in liquefled form, and thereafter cooling the mixture, releasing the pressure, and separating an ethylated benzene product therefrom.

10. In a method of making ethylbenzene, the

steps of forming a, liquefied mixture of benzene,

ethylene, and aluminum chloride in amount corresponding to between 0.3 and 1.0 per cent of the weight of the benzene, heating the mixture to a reaction temperature between 90 and 200 C. while at a pressure suiiicient to maintain the same largely in liqueed form, and thereafter cooling themixture, bringing it to atmospheric pressure and separating ethylbenzene therefrom.

11. In a continuous method of4 ethylatin'g` 10 benzene, the steps of passing benzene over solid aluminum chloride at a rate such that aluminum chloride is dissolved in amount corresponding to between 0.3 and1.2 per cent of the weight of the benzene, passing ethylene into the solution under a pressure suflicient to liquefy the mixture which is formed, passing the mixture through a heating zone where it is heated to a reaction temperature between and 200 C. while under Ypressure suiicient to maintain the same in liqueed form, cooling the mixture and bringing it to atmospheric pressure as itflows Yfrom said heating zone, and separating an ethylated benzene compound from the mixture.

12. In a continuous methodfor manufacturing ethylbenzene, the steps of passing benzene over solid aluminum chloride at a rate such that f aluminum chloride is dissolved in amount corresponding to between 0.3 and 0.7 per cent of the weight of the benzene, admixing ethylene with the resultant solution Lunder a pressure suicient to liquefy the mixture and in amount such that the mixture contains at least 2 molecular equivalents of benzene per mole the ethylene, passing the mixture through a reaction zone where it is heated to a reaction temperature betewen 90 and 200 C. while at a pressure sufficient to maintain the same in liquefied form,

cooling the mixture and bringing it to atmospheric pressure while owing from said reaction zone, and thereafter separating ethylbenzeneY from the mixture.

13. A method, as described in claim 12, wherein a polyethylbenzene product is admixed with ethylene and benzene and returned to the reaction zone.

14.4 A method, as described in claim 12 wheref in the polyethylbenzene products are admixed with ethylene and benzene and returned to the reaction zone.

15. In a continuous method of ethylating benzene, the stepsoi' admixing ethylene, benzene and aluminum chloride in relative proportions such that the mixture contains at least two molecular equivalents of benzene per mole of the ethylene and contains the aluminum chloride in amount corresponding to between 0.3 and 1.0 per cent of the weight of the benzene, applying to the mixture sucient pressure to liquefy the same, passing the'mixture at such ypressure through a reaction zone where it is heatedto a reaction temperature between and 200 C., Vcooling and releasing the pressure on'the mixture flowing from the reaction zone, distilling ethylbenzene from the reacted mixture, and returning a portion of the residual mixture of polyethylbenzenes and complex catalyst to the reaction zone together with the benzene and ethylene reactants and sufficient added aluminum chloride so that the mixture within the reaction zone contains between 0.00175 and 0.00584 molecular equivalent of aluminum chloride in the catalyst per mole of the aromatic compounds.

16. A methodas described in claim 15, wherein the hot reaction .mixture owing from the reaction mixture is passed into a zone of lower pressure so asY to distill benzene and ethylbenzene therefrom. n

EDGAR C'. BRITTON. JOI-IN C. VANDER WEELE. 

